Drip irrigation hose and method of its manufacture

ABSTRACT

The serpentine, turbulence inducing path lengths from the inlets to the outlets of the flow regulating passage of a continuous emitter drip irrigation hose are arranged in back to back fashion relative to the outlets in the sense that the chevrons angle away from each of outlets, so there is parallel turbulent flow from two inlets to each outlet. This doubles the flow rate from each outlet without changing the dimensions of the flow regulating passage.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of application Ser. No. 08/346,335, filedNov. 29, 1994, now abandoned, which in turn is a continuation-in-part ofapplication Ser. No. 08/249,904, filed May 26, 1994, now abandoned.

FIELD OF THE INVENTION

This invention relates to the field of drip irrigation and, moreparticularly, to a turbulent, high flow drip irrigation hose and methodfor its manufacture.

BACKGROUND OF THE INVENTION

Drip irrigation hose can be classified as having either discreteemitters or continuous integral emitters. An example of discreteemitters is shown in U.S. Pat. No. 4,850,531. An example of continuousintegral emitters is shown in U.S. Pat. No. 4,247,051.

A design objective of drip irrigation hose is uniformity of the driprate from each emitter. Since the water pressure in a drip irrigationsystem varies as a function of elevation of the field, it is customaryto incorporate a pressure regulating mechanism into the emitters.Turbulent flow is less sensitive to pressure variation than laminarflow. Accordingly, it has become common practice for drip irrigationhose to employ a serpentine flow regulating passage as continuousintegral emitters to promote turbulent flow. An example of such dripirrigation hose is disclosed in U.S. Pat. No. 4,984,739, where a seriesof staggered, upstream angled chevrons or weirs form the serpentinepassage.

In a typical drip irrigation hose with continuous integral turbulentflow emitters, the emitters comprise a flow regulating passage formed byribs that also seal the overlapping margins of an elongated bent sheetof plastic film. The passage is divided by cross ribs to form flowregulating segments. The bent film forms an elongated water supplypassage having a large diameter. An inlet is formed from the watersupply passage to one end of each segment of the flow regulatingpassage. An outlet is formed from the other end of each segment of theflow regulating passage to the exterior of the hose. Between the inletand outlet, each segment has staggered, upstream angled chevrons.

Complications can occur when the dimensions of this type of dripirrigation hose are changed to increase the flow rate. Generally, theflow rate can be increased by decreasing the length of the segments,increasing the height of the ribs, or increasing the separation betweenthe ribs of the flow regulating passage. However, these measures tend todecrease the reliability and uniformity of the product and to cause thewater to squirt out of the outlets because the line pressure is notfully dissipated by the flow regulating passage.

SUMMARY OF THE INVENTION

According to the invention, the serpentine, turbulence inducing pathlengths from the inlets to the outlets of the flow regulating passage ofa continuous emitter drip irrigation hose are arranged in back to backfashion, so there is parallel turbulent flow from two inlets to eachoutlet. This doubles the flow rate from each outlet without changing thedimensions of the flow regulating passage. In other words, the flow ratefrom each outlet is twice the flow rate of a single path from inlet tooutlet. Specifically, a longitudinal flow regulating passage having asmall cross section is disposed along a elongated water supply passagehaving a large cross section. There are plurality of longitudinallyspaced inlets from the water supply passage to the flow regulatingpassage and a plurality of longitudinally spaced outlets from the flowregulating passage to the exterior of the hose. The outlets are offsetfrom the inlets to provide two substantial path lengths from each inletto a respective outlet. A series of staggered chevrons are formed alongthe sides of the flow regulating passage. The chevrons are angledtowards the inlets along each path length to induce turbulent flow.Specifically, a longitudinal flow regulating passage having a smallcross section is disposed along a elongated water supply passage havinga large cross section. There are plurality of longitudinally spacedinlets from the water supply passage to the flow regulating passage anda plurality of longitudinally spaced outlets from the flow regulatingpassage to the exterior of the hose. The outlets are offset from theinlets to provide two substantial path lengths from each inlet to arespective outlet. A series of staggered chevrons are formed along thesides of the flow regulating passage. The chevrons are angled towardsthe inlets along each path length to induce turbulent flow.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of specific embodiments of the best mode contemplated ofcarrying out the invention are illustrated in the drawings, in which:

FIG. 1 is a top plan view of a drip irrigation hose incorporating theprinciples of the invention with the outer margin partially cut away;

FIG. 2 is a sectional view taken through plane 2--2 in FIG. 1illustrating two inlets to the flow regulating passage;

FIG. 3 is a sectional view taken through plane 3--3 in FIG. 1illustrating an outlet from the flow regulating passage;

FIG. 4 is a schematic block diagram of the method for manufacturing thedrip irrigation hose shown in FIG. 1; and

FIG. 5 is a perspective view of apparatus for performing the beadlaying, rib forming, film folding, and regulating passage forming stepsof FIG. 4.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT

The disclosures of U.S. Pat. Nos. 4,247,051 4,984,739 and 5,123,984 areincorporated fully herein by reference.

As illustrated in FIGS. 1, 2 and 3, a drip irrigation hose 10 is formedfrom a thin (e.g., 4 to 15 mil) film 12 of flexible water imperviousplastic material bent along its length to form an overlappinglongitudinal seam between opposing longitudinal margins, namely an innermargin 14 and an outer margin 16. Margins 14 and 16 are sealed togetherby a continuous repeating pattern of longitudinally extending spacedapart ribs 18 and 20 made of the same or compatible plastic material asfilm 12. Ribs 18 and 20 and margins 14 and 16 define a flow regulatingpassage 22 as described in more detail in the referenced '051 and '739patents. A water supply passage 24 is defined by the remainder of film12. At spaced intervals, rib 18 has a series of interruptions andpillars that form inlets 26 to flow regulating passage 22. Midwaybetween each pair of inlets 26, an outlet 28 is formed by one or moreholes in outer margin 16. A series of staggered chevrons 30 are formedalong the inner sides of ribs 18 and 20 between each of inlets 26 andoutlets 28. In each case, the chevrons are angled toward inlets 26 topromote turbulent flow along the path length from each inlet 26 tooutlet 28 of flow regulating passage 22. As illustrated in FIG. 1,inlets 26 have a substantially larger cross sectional area than outlets28 and the flow regulating passages. As a result, inlets 26 are not flowlimiting. Thus, the serpentine turbulence inducing path lengths arearranged in back to back fashion relative to the outlets in the sensethat the chevrons angle away from each of outlets 28, so there isparallel flow throughout the length of hose 10 from two of inlets 26 toone of outlets 28. The pattern of ribs illustrated in FIG. 1 is repeatedcontinuously along the entire length of hose 10 between overlappingmargins 14 and 16. As a result, outlets 28 are spaced from each otherand offset from inlets 26, which are also spaced from each other. Sinceinlets 26 are not flow limiting, of inlets 26 feeds two of outlets 28and each of outlets 28 is fed by two of inlets 26. As a result, the flowrate through each outlet 28 is doubled because it is fed by two inletsand two flow regulating passages.

In summary, as described above, since the pattern of ribs shown in FIG.1 is repeated continuously along the entire length of hose, each ofinlets 26 feeds two outlets 28. In other words, the inlet 26 shown onthe left side of FIG. 1 feeds the outlet 28 shown in FIG. 1 and theadjacent outlet 28 of the pattern to the left of what is shown in FIG. 1and the inlet 26 shown on the right side of FIG. 1 feeds the outlet 28shown in FIG. 1 and the adjacent outlet 28 of the pattern to the rightof what is shown in FIG. 1. However, the water flow from each inlet 26through the flow regulating passages 22 is not cut in half orsubstantially reduced, because inlets 26 are not flow limiting. To thecontrary, the flow rate is substantially doubled without changing thedimensions, as compared to the case where the inlets are flow limitingor the case where one inlet feeds one outlet.

In operation when hose 10 is pressurized in the field, water flowsthrough supply passage 24 to inlets 26, passes from inlets 26 throughflow regulating passage 22 to outlets 28, and exits from outlets 28 tothe exterior of hose 10. Two back to back path lengths are formed fromadjacent pairs of inlets 26 to each outlet 28, thereby doubling the flowrate for the dimensions of the flow regulating passage, i.e., pathlength, rib height and rib spacing, vis-a-vis the drip irrigation hosedisclosed in the '739 patent. It should be noted that cross ribsdividing the flow regulating passage into segments as disclosed in the'739 patent are not required in the practice of the invention. Suchcross ribs could be provided, however, if desired at inlets 26 (oroutlets 28), effectively dividing each inlet 26 (or outlet 28) into twoinlets (or outlets), one for each adjacent segment of the flowregulating passage.

The method for making the described drip irrigation hose is illustratedin FIGS. 4 and 5. As represented in FIG. 4 by a block 40, outlets 28 arefirst formed in film 12 in the manner disclosed in the '984 patent orU.S. Pat. No. 5,522,551, which issued on Jun. 4, 1996, the disclosure ofwhich is incorporated fully herein by reference. Then, as represented bya block 42 inner margin 14 is folded. As represented by a block 44, oneor more beads are laid on the outside surface of inner margin 14 by oneor more extrusion nozzles. As represented by a block 46, a pattern ofribs, i.e., ribs 18 and 20, is formed by a molding wheel. As representedby a block 48, outer margin 16 is next folded onto inner margin 14 withthe formed ribs therebetween. Finally, as represented by a block 50,flow regulating passage 22 is finished by passing inner margin 14, outermargin 16, and the ribs 18 and 20 through the nip of a form wheel and abacking wheel to set precisely the height of ribs 18 and 20. This methodis described in more detail in the '984 patent.

FIG. 5 illustrates apparatus for performing the steps represented byblocks 44 to 50. One or more extrusion nozzles 52 deposit one or morecontinuous longitudinal beads 54 on the outside surface of inner margin14. Film 12 then passes through the nip of a rotating molding wheel 56and a rotating backing wheel 58. Molding wheel 56 has a pattern ofdepressions 60 corresponding to the desired rib pattern on dripirrigation hose 10, i.e., the pattern shown in FIG. 1. In the nip ofwheels 56 and 58, beads 54 are shaped by molding wheel 56 to form thedesired bead pattern repeatedly and continuously on film 12 for theentire length of hose 10. Thereafter, external margin 16 of film 12 isfolded by a guide 62 to overlap inner margin 14. As a final step, theoverlapped margins of film 12 pass through the nip of a form wheel 64and a backing wheel 66. Form wheel 64 has a groove 68 that depresses theribs formed by beads 54 to set the rib height at a specified value thatdetermines the flow rate of the hose. During the described process, film12 is continuously transported by conventional means not shown. Forexample, the disclosed wheels could be driven or other drive wheelscould be provided to transport the film.

The described embodiment of the invention is only considered to bepreferred and illustrative of the inventive concept; the scope of theinvention is not to be restricted to such embodiments. Various andnumerous other arrangements may be devised by one skilled in the artwithout departing from the spirit and scope of this invention.

What is claimed is:
 1. A drip irrigation hose made from a waterimpervious material comprising:an elongated water supply passage havinga large cross section; a longitudinal flow regulating passage having asmall cross section, the flow regulating passage being disposed alongthe water supply passage; a plurality of longitudinally spaced non flowlimiting inlets from the water supply passage to the flow regulatingpassage; a plurality of longitudinally spaced outlets from the flowregulating passage to the exterior of the hose, the outlets being offsetfrom the inlets to provide two substantial path lengths from each inletto a respective outlet; and a series of staggered chevrons formed alongthe flow regulating passage, the chevrons being angled toward the inletsalong each path length to induce turbulent flow.
 2. The hose of claim 1,in which the water supply passage comprises an elongated strip ofplastic film folded lengthwise to form an overlapping seam from opposingouter and inner margins of the film and a seal between the margins inthe overlapping seam.
 3. The hose of claim 2, in which the flowregulating passage comprises a continuous repetitive pattern of plasticribs extending between the margins in the overlapping seam to form theseal.
 4. The hose of claim 3, in which the pattern of ribs includes alongitudinal rib facing the water supply passage and the inlets eachcomprise one or more interruptions in the rib.
 5. The hose of claim 4,in which the outlets each comprise one or more holes in the outermargin.
 6. The hose of claim 3, in which the pattern of ribs includesfirst and second parallel longitudinal ribs having inner sides that faceeach other, the chevrons being formed along the ribs.
 7. A dripirrigation hose made from a water impervious material comprising:anelongated water supply passage having a large cross section; alongitudinal flow regulating passage having a small cross section, theflow regulating passage being disposed along the water supply passage; aplurality of longitudinally spaced inlets from the water supply passageto the flow regulating passage; a plurality of longitudinally spacedoutlets from the flow regulating passage to the exterior of the hose,the outlets being offset from the inlets to provide two substantial pathlengths from each inlet to a respective outlet; and the inlets having asubstantially larger cross sectional area than the outlets and the flowregulating passages such that each outlet is fed by two inlets and twoflow regulating passages.
 8. The hose of claim 7, in which the flowregulating passage comprises a continuous repetitive pattern of plasticribs extending between the margins in the overlapping seam to form theseal.
 9. The hose of claim 8, in which the pattern of ribs includes alongitudinal rib facing the water supply passage and the inlets are eachformed by a plurality of interruptions in the rib, leaving between theinterruptions pillars.
 10. The hose of claim 9, in which each inletfeeds two outlets.
 11. The hose of claim 7, in which each inlet feedstwo outlets.